React hot loader for TypeScript

A lightweight, Typescript-native, Babel-free, plugin-free, implementation of react-hot-loader.

Add React hot-reload (live update without losing state) in your TypeScript projects!

Supported bundlers

• Webpack + ts-loader
• FuseBox

Features

• Compile-time transformation is done using a TypeScript compiler hook,
• Supports both React component classes and functional components,
• Reliable hot-reload feature based on Dan Abramov's react-proxy (for ES5) or react-stand-in for ES6 (needs alias),
• Support both ES5 and ES6 compilation targets.

Bonus

• Rewrites arrow functions to be hot-reload friendly (can be opt-out),
• Ensures React functions and classes have a "display name", for enhanced debugging experience.

Installation

npm install react-hot-ts -D

Or

yarn add react-hot-ts -D

Webpack configuration

Just 2 steps:

1. Make your Webpack configuration "hot" for development

   See guide: https://webpack.js.org/guides/hot-module-replacement/#enabling-hmr

2. Configure the TypeScript loader with a custom transformer (you can keep it in your production builds)

const rhTransformer = require('react-hot-ts/lib/transformer');
/*...*/

module.exports = {
    /*...*/
    rules: [
        {
            test: /\.tsx?$/,
            use: [{
                loader: 'ts-loader',
                options: {
                    // enable TS transformation
                    getCustomTransformers: {
                        before: [ rhTransformer() ]
                    }
                }
            }]
        }
        /*...*/
    ]
    /*...*/
}

Transformer options

Although they shouldn't be needed for normal use cases, the transformers has a few options:

Usage: rhTransformer(options)

Where options is an object with the following optional fields:

• disable: force release mode, disregarding NODE_ENV value,
• keepArrows: opt-out of arrow functions rewriting; this can avoid a lot of extra code (and maybe subtle issues) when targeting ES5 instead of ES6,
• rhRuntime: (advanced) specify an alternative module to be required for the client hot-loading runtime logic.

Example: rhTransformer({ keepArrows: true })

Attention NODE_ENV

You must set the NODE_ENV environment (e.g. process.env.NODE_ENV) to "production" to disable the transform. You will see this message in the console:

[react-hot-ts] disabled for production

Note: Webpack's mode is not sufficient.

React usage

Once the compiler transformation is in place, you just need to wrap your root ReactDOM.render call:

import { hot } from 'react-hot-ts';

hot(module)( ReactDOM.render(<App/>) );

When building for release, only the HMR runtime will be replaced by a no-op.

Now run Webpack dev server and enjoy live component updates!

Known issues

Targeting ES6

If you target ES6 with the TypeScript compiler, you will run into runtime errors like:

Uncaught TypeError: Cannot convert undefined or null to object

The reason is that react-proxy isn't ES6-friendly, and the solution is to install react-stand-in and add an alias in your bundler to remap the former:

• https://webpack.js.org/configuration/resolve/#resolvealias
• https://fuse-box.org/docs/development/configuration#alias

Only .tsx files are considered

If you use .ts and manual React.createComponent code, it won't be registered for HMR.

Workaround is to use .tsx ;)

Passing non-exported React classes/functions references

Non-exported class or function won't be reloaded if their reference is kept outside the module.

// A.js
class A extends Component {...};
export function provideA() {
    return A;
}

// B.js
import {provideA} from 'A';
export class B extends Component {
    private ARef;
    constructor() {
        this.ARef = provideA();
    }
    render() {
        return <ARef/>;
    }
}

Workaround is to export the class/function even if it won't be used from exports.

ISC License

Copyright 2019 Philippe Elsass

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.